In a series of crosses to look at the relationship of different genes with each
ID: 319073 • Letter: I
Question
In a series of crosses to look at the relationship of different genes with each other, the following crosses were performed. The numbers of offspring obtained from each cross are shown.
Cross offspring linkage?
AaBb x aabb 20 AaBb, 15 Aabb, 18 aaBb, 17aabb
CcDd x ccdd 54 CcDd 49 ccdd, 98 Ccdd, 101 ccDd
EeFf x eeff 43 EeFf 7 Eeff 42 eeff 5 eeFf
a) For each one, note whether the genes are linked, and if so how closely (in mu); and whether the alleles are present in coupling or repulsion in the heterozygous parent.
b) Which genes are most tightly linked (closest together on the same chromosome)?
Explanation / Answer
Answer:
Cross offspring linkage?
AaBb x aabb 20 AaBb, 15 Aabb, 18 aaBb, 17aabb No linkage as the test cross progeny are in 1:1:1:1 ratio.
CcDd x ccdd 54 CcDd 49 ccdd, 98 Ccdd, 101 ccDd Alleles are in repulsion. linkage is 34.1 mu. The alleles, Cd on one chromosome and cD alleles on their homologous chromsome are linked.
EeFf x eeff 43 EeFf 7 Eeff 42 eeff 5 eeFf Alleles are in coupling. Linkage is 12.37 mu. The alleles, ED on one chromosome and ed alleles on their homologous chromsome are linked.
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